Messages in this thread | | | Date | Thu, 18 May 2006 11:37:18 +0200 | From | "Jan Beulich" <> | Subject | Re: [discuss] Re: [PATCH 2/3] reliable stack trace support (x86-64) |
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>>> Andi Kleen <ak@suse.de> 16.05.06 19:05 >>> >On Tuesday 16 May 2006 18:06, Jan Beulich wrote: >> >>> Andi Kleen <ak@suse.de> 16.05.06 17:13 >>> >> On Tuesday 16 May 2006 16:21, Jan Beulich wrote: >> >> These are the x86_64-specific pieces to enable reliable stack traces. The >> >> only restriction with this is that it currently cannot unwind across the >> >> interrupt->normal stack boundary, as that transition is lacking proper >> >> annotation. >> > >> >It would be nice if you could submit a patch to fix that. >> >> But I don't know how to fix it. See my other mail >which mail?
Reply to Ingo (with you on cc) regarding patch 1/3. Just saying that I don't know much about expressions here.
>> - I have no experience with expressions, nor have I ever seen them in >> use. > >I remember Jim Houston used a hack of just loading the old stack into a register >and defining that as a base register in CFI. I guess i would be willing >to trade a few moves for that (should be pretty much free on a OOO CPU anyways) >You think that trick would work?
I don't think that would, because without CONFIG_DEBUG_INFO none of the preserved registers get saved, hence there's no register to use for this. Thus the price would not only be a move, but also a save/push and a reload/pop.
>> >> +#define UNW_PC(frame) (frame)->regs.rip >> >> +#define UNW_SP(frame) (frame)->regs.rsp >> > >> >I think we alreay have instruction_pointer(). Better add a stack_pointer() >> >in ptrace.h too. >> >> I could do that, but the macros will have to remain, as they don't access pt_regs directly, so I guess it'd be >> pointless to change it. > >UNW_PC() is instruction_pointer(&frame->regs), isn't it?
Yes. But the intention is that the user of UNW_PC doesn't need to know any details of what fields frame has (i.e. the parameter of UNW_PC must only be frame), so you can't replace it with instruction_pointer().
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